$ { \left[\begin{array}{rr}{1} & {-1} \\ {-2} & {-2} \\ {0} & {0}\end{array}\right]+\left[\begin{array}{rr}{-1} & {-1} \\ {-1} & {0} \\ {4} & {2}\end{array}\right] = {?} } $
Answer: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{1}+{-1} & {-1}+{-1} \\ {-2}+{-1} & {-2}+{0} \\ {0}+{4} & {0}+{2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {-2} \\ {-3} & {-2} \\ {4} & {2}\end{array}\right]}$